dsavitsk

Yes, the front switch. On the DSHA-1 it changes whether the two output windings are in parallel or series. The transformers are 1+1:1+1 (quadfilar). The inputs are always in parallel, so when the outputs are in parallel, the transformer is 1:1. When they are in series, they are 1:2. The Zout of the circuit itself is very low. The Z difference is due to the copper in the transformer. This is true with all transformer coupled amps -- they all have added Z due tot he copper. The jumpers change the gain. As a byproduct, they also change the input impedance, but not in a way that will make any difference for 99% of sources.

The high Z out is right around where the Senn amp is. The Lo is about 1/4 as much. I tend to think they sound better with the high one, but it is really a matter of preference.

A transformer coupled tube amp with a 300R secondary is likely going to be right in this ball park.

This has been in the back of my head -- this build reminds me of one of my favorite builds I've seen. http://www.diyaudio.com/forums/attachments/tubes-valves/144849d1256750797-photo-gallery-dsc_0617.jpg

It's a really beautiful build. Ask 10 designers how to build an amp with those parts, and you might get 20 designs. 9 of them will give you the same design, and one will give you 11 different ones. The point being that if this is a "traditional" amp, then what the schematic looks like is probably pretty easy to deduce, but there are lots of ways of tinkering with the details.

Happy Birthday Ari!

Happy Birthday!

The availability of inexpensive circuit boards has been a blessing, and a curse. This is just the crap I don't know what to do with. Note the original Millett Hybrid on the far left

I don't totally disagree. I did a very basic version of the mod just using some wool felt I had left over from a speaker project. There was definitely less treble energy, but there was also a flatness that made them a bit boring (hence the HD650 comment). And bass seemed to be reduced. Since the mod can clearly be implemented better, I'll reserve any judgment until I actually do it right. I do like them stock with the right amp. Tyll -- have you measured them with different amps, or just with some low Z high feedback type?

It was a facetious comment.

Not sure if it is useful to anyone, but I edited Tyll's pattern to make the lines thicker and get rid of the extra stuff. The reason being that you can use the toner transfer method to transfer this directly onto (wool) felt to make cutting easier. The moment between a decently transferred image, and burned piece of felt is short. These now sound more like my HD650s ... not sure that's a good thing here SennheiserHD800modTemplateEDIT.pdf

I finally bought some HD800s. I don't buy many headphones so this was a big deal. I was talking to someone today, and he asked if the whole cup was the speaker. I then realized that the whole outer shell is supposed to look like a speaker cone. Maybe everyone else knew this, but I had never noticed. They still sound good, but they went from ugly to lame.

It's perfect here today -- we only get a few of these each year. I'm quitting early to go play tennis. It looks like typical Chicago spring weather for the next week or so.

Crime is not any higher than it was in the good old days -- probably lower. It is just more publicized. It is sad that our misconceptions lead us to be less good to people, which probably feeds that misconception. Good on you Steve. A few years ago, my wife's coworker need his car jumped. It was January in Chicago. 10 degrees, dark, snowy. They could not find the lever to open the hood on our car. He (the coworker) found a lever and pushed it really hard. When nothing happened, he pushed it even harder and managed to rip the steering wheel tilt lever right off the steering column. Our steering wheel bounced up and down for a month until we paid $1000 to fix it. Repair place said they had never seen such a thing. The coworker never even offered to help and made some lame argument about how it wasn't his fault since it wasn't his car.

Did this make anyone else think about the Coase Theorem?

Happy Birthday!

Happy Birthday!

Not the nicest part of the city Downtown, or maybe Hyde Park (by the U. of Chicago). John and Brian both live closer and can probably help more.

Maybe some pics? I am totally stumped on what the problem is -- perhaps because EL84's have 9 pins ...

Ha Ha, I just got the joke.

Early this morning in Chicago:

more ...

Thanks. I would attribute any success to the teacher. My grandfather, and his father, were blacksmiths, so I grew up with some of their work around the house -- I have a deeper appreciation for it now. I also played 2 hours of tennis afterwards, so I am feeling it today.

Have a great one!

I took a blacksmithing class and made a fire pokey. Now I need to get a fireplace.